A liquid mixing device for mixing multiple eluents into a mobile phase is used in a gradient elution method in a liquid chromatograph. The liquid mixing device is hereinafter referred to as a mixer. There are a mixer with a structure that is filled with beads in the form of small particles and a mixer with a structure in which a hole and a groove are formed on a substrate to serve as a flow channel. Among these, since the mixer with the structure that uses the flow channel may mix eluents using a small flow channel volume, the mixture time is short and the analysis time is short.
The structure is disclosed in PTL 1, which changes the cross-sectional shape of a branched flow channel at a branch point and at a junction point, in terms of the structure of the flow channel that facilitates the mixing using the branch and the junction of the flow channel. According to this structure, since the direction in which the liquid flowing through the flow channel branches and the direction in which the liquid flowing through the flow channel joins together change and an interface area of two liquids increases every branch and junction, a mixture effect is facilitated.
The method is disclosed in PTL 2, in which a specific change in concentration is caused in a gradient elution method mobile phase by the multiple flow channels through which the times for the liquid to pass are different and by a combination of the liquid sending timings of a liquid sending pump.